1. Technical Field
The present invention relates in general to a self-healing coupler for a serial RAID device and in particular to a self-healing coupler for a serial storage architecture wherein the self-healing coupler by-passes any disk drive or drives in which communication or link has been broken and re-couples to allow and maintain the serial link between all remaining disk drives. Still more particularly, the present invention relates to a switching device for a serial device that switches to a by-pass mode to by-pass the serial device when communication or link of the device has been broken and to an in-line mode for maintaining the device as serially linked to the other devices when communication or link of the device is active and has been maintained.
2. Description of the Related Art
FIG. 1 shows a conventional serial storage architecture (SSA) RAID system 10. The SSA RAID system 10 has a number of target disk drives 12 (i.e. targets 1, 2, and 3 as shown in FIG. 1) serially linked together, and the target drives 12 are linked to a SSA initiator 14. Problems arise when a break in communication or link occurs at any of the target drives 12. FIG. 1 shows that a break 18 of communication or link has occurred at target 1. The serial communication or link has therefore been broken between target 1 and the other serially linked devices, targets 2 and 3, and the SSA initiator 14 and a host computer in communication with the SSA initiator 14 may no longer be able to access the other serially linked target drives 2 and 3, such as to access the data stored therein. Therefore, the other serially linked target drives, such as target drives 2 and 3, typically cannot be accessed until the communication or link problem has been identified and fixed or another access route of the other serially linked target drives are configured. Also, when a break in communication or link occurs, the serial storage architecture is not maintained, and thus the host computer may not be able to recognize the SSA RAID system 10.
It would therefore be advantageous and desirable to have a device for maintaining the serial link between devices when a break in communication or link at one of the devices has occurred. It would also be advantageous and desirable to provide switching of a serial device with a communication or link problem from an in-line mode in which the serial device is serially linked to other devices to a by-pass mode in which the serial device is by-passed and the other devices are re-coupled and serially linked together. It would be advantageous and desirable to provide a self-healing coupler for a serial storage architecture wherein the self-healing coupler by-passes any disk drive or drives in which communication or link has been broken and re-couples and serially links all remaining active disk drives.
It is therefore one object of the present invention to maintain the serial link between devices when a break in communication or link at one of the serially linked devices has occurred.
It is another object of the present invention to by-pass any serially linked disk drive or drives in which communication or link has been broken and re-couples to maintain serial link between all remaining disk drives.
It is yet another object to self-heal the coupling in a serial storage architecture when a communication or link has been broken wherein any serial device or disk drive or drives in which communication or link has been broken is by-passed and all remaining active devices and disk drives are re-coupled to maintain serially link between the devices.
It is another object of the present invention to provide an override system for manually controlling a serially linked device in a by-pass mode or an in-line mode.
The foregoing objects are achieved as is now described. A self-healing coupler for a serially linked device that is serially coupled to other devices. The serially linked device has a communication input and a communication output. The self-healing coupler has at least one switching device coupled to the communication input and the communication output of the serially linked device, a communication detection device coupled to the communication output of serially linked device for detecting continuous communication at the communication output, and a switch coupled to the at least one switching device. The switch controls at least one switching device. The serially linked device is maintained linked and in an in-line position to the other devices when the continuous communication has been detected at the communication output. The serially linked device is in a by-pass position from the other devices and the other devices are maintained as serially linked together when the continuous communication has not been detected at the communication output. The serially linked device has bi-directional communication lines. A pair of polarized communication lines provide communication in one direction through the serially linked device and another pair of polarized communication lines provide communication in another direction through the serially linked device. An override system is coupled to the switch to allow manual control of the switch in controlling the at least one switching device to manually maintain the serially linked device between the in-line position and the by-pass position.